1. Technical Field
The present invention relates to processing digital signals, and more particularly, to compensating for chromatic dispersion and polarization mode dispersion in digital signals.
2. Description of the Related Art
In an optical communication system, chromatic dispersion and polarization mode dispersion may distort a transmitted signal. However, these abnormalities in the signal may be corrected at the receiver. While adjustments for chromatic dispersion may be fixed for a given channel, adjusting a channel for polarization mode dispersion involves dynamically adjusting the signal using channel estimates. In conventional systems, the equalization of an input signal is processed block-by-block, with each block having a fixed size that is equal to the block size utilized by the fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT). As equalization is performed on a block-by-block basis, the output signal may be used as feedback for estimating channel parameters.
However, a problem arises due to the fact that channel parameters are estimated using feedback from the output signal. Since the equalization scheme processes the signal on A block-by-block basis, the channel parameters used in compensating for polarization mode dispersion can only be updated once every FFT block size. Given that the FFT block size can be relatively large, the updating speed may be very slow, thus resulting in slow channel tracking capability.